Robert Simmons

Greetings, I have been reading more about the Hofi technque and the hammer that is encouraged for that technique. Now I plan to get the DVD and then maybe the hammer after I see the DVD when finances permit but I have some questions in the meantime that I was hoping practitioners of Mr. Hofi's tecnique could answer. 1) What is the essential difference between the Hofi technique and what "standard blacksmithing" technique (if there is such a thing) is. I know Hofi's is suppoesed to be more ergonomic but how so? 2) Is the Hofi technique something a smithing beginner like I could learn or does it require a lot of experience to even understand? Does it involve learning some different muscle memory about swinging a hammer? 3) Is the technique hard to learn for experienced smiths because of muscle memory? For example, it can be very difficult to change an experienced golfer's technique due to years of muscle memory. 4) Is the Hofi technique just concerned with hammering or are there other spects such as usage of tongs and strategy for adressing projects? 5) Can the Hofi technique be employed with hammers other than the Hofi hammer even if imperfectly? The hammer itself can be quite pricey and may intimidate newbies who are not rolling in cash. If it can be practiced with other hammers, which ones? 6) Does Hofi have a book out or plans to write one? Thanks in advance. -- Robert

*shrug* I was just trying to help. I spent three weeks playing with this stuff 6 to 10 hours a day. Running a burner in a forge isnt the same as melting something with it. At this point I will just say "good luck" and move on.

Not really just easier airflow or the larger the venturi the better the torch would perform and that isnt always true. I have tried all sorts of combos. By the Venturi principal mathematics, the velocity is porportional to the constriction ratio. Think of it this way, in the large size of the cone there is X area capable of pulling some volume of air per second. When you introduce the venturi, that volume of air must still be pulled through the pipe but in order to do so it MUST speed up because air flow is a function of velocity times area. The gas pipe is firing propane gas into the tube and accelerating, generating a low pressure area in the pipe. The surrounding air must compensate but the pressure is all forwards so air must come in the back. The air rushes in from the back to fill the low pressure and then must be accelerated to maintain the same flow per second as it had when it was in a large tube. When the acceleration of the air equals the flame front velocity, you have a stable burner. The real problem you will run into is when you stick that into the forge. The air pressure drops initially as it should and air is accelerated into the chamber but the problem is most of the air in our atmosphere is inert and doesnt burn. Only the oxygen burns leaving 79.05% or so of nitrogen and other parts blowing at high speed into the forge. This air has nowhere to go except out the door. So in the forge the air pressure will rise and eventuallt start to counteract the higher airpressure on the other side of the venturi. The back pressure eventually cancells out the venturi pressure and the flame burns without enough oxygen (rich) or goes out altogether. So then the race is on to find a way to inject more oxygen while keeping the back pressure from cancelling out the venturi. If you can put enough oxygen in to get a complete burn of the propane then back pressure wont be an issue because the propane wont be able to slow down as it is consumed so fast, furthermore the high temperature in the forge will reduce the pressure of the air. DO NOT TRY TO INJECT AIR FROM A WELDER'S O2 BOTTLE! If you do, we will be reading about your house exploding on the evening news. You do not want to go down that route. My solution was to try to go to a blown burner to counteract the back pressure and feed the flame more o2 at this high altitude. There were numerous problems with flame front velocity not being fast enough to counteract the blown force. After thinking about it, it doesnt surprise me because again 79.05% of the gas is inert. What I needed was a way to introduce more air without pushing the flame front off the end of the torch. Hence the idea to introduce the air directly into the chamber. You would get a venturi there but you would find the gas doesnt have enough time to accelerate and mix with the air. Also remember you want that jet shooting into the cone so the gas is sped up as well. The pressure from the bottle is the driver here and the gas will have already slowed down considerably before it hits the venturi on the end. In addition you will need something like a flame stabilizer on the end. Flares are all well and good until they go red and then yellow in the forge. A flame stabilizer will negate the need for the flame holder and then it will slow down the mix by means of turbulence on the side while allowing the center mix to get through unobstructed. The flame will be stabilized because the gas will want to push the flame front off the end in the middle but will be too slow and want to burn back where the turbulence is. The balance stabilizes the flame just a fraction of an inch off the end of the tube. P.S. When you put the burner in the forge, everything will change and leave you thinking a lot more.

Do you practice it yourself? Are you saying I could make do with the czech hammer for now?

My question would be if you can use the technique without his hammer. I would love to get one of his but it just inst in the budget. On the otherhand blacksmith depot has a "Hofi Syyle" czech hammer that is within my budget. Could I get one of those and the video and get started and move to the premium hammer later? Since I am new to smithing I suppose now would be the right time to get the technique rather than after i have ingrained several habits.

The T-Rex has a machined internal venturi. Without a venturi, it wont matter as the flame front velocity will outrun he gas velocity. Look at the pic above and you see the constriction on the burner tube? There is your venturi.

From my experimentation I am pretty sure that it is the lack of the constriction that is your problem You want the gas to be blown into a conical constriction. This would take advantage of the venturi principal and speed up the gas flowing through the tube into the burner. Right now your mix is taking place early and the burn is taking place immediately on the end of the supplied mix. So your flame front velocity exceeds your gas velocity and that means it will burn back until it runs out of air to mix with which is justi n front of your injector. You will need to have the gas get injected before a restriction and then you can asdjust how far from the constriction. You can accomplish this as I did with a reducing pipe or you can use castable refractory and two cones to cast the venturi right into the burner.

Well I now have a video up of the forge in operation. Let me know what you think.

Thanks for the great tips and advice. As for the above comment, I was generally following a pattern on the internet at anvilfire. But I have two problems right now. First of all, I dont have the correct stock that I need to do it exactly as shown and finances are a little thin right now as I ended up spending way too much getting the forge up. When I get paid on the 25th I intend to get some more stock to make it easier. As it is, all I have is 1/4inch round, 3/8ths square and a bunch of tubing and sheet. So I am merely trying to improvise with what i have knowing I will mess up the first few times badly. Perhaps with the stock I have, I should be trying something else. I tried to do upset on the 1/4 inch rod to make rivets or nails but I ended up just bending the entire rod unfortunately. I am just a newbie so I figure I will botch several things before I get something good. Inexpensive hammer but not big box store, it is a forging hammer. A farrier's hammer. I will do some reading on how to dress it. As for hammer control, can you be more specific? Do you mean just accuracy in hitting or is there some other aspect I could focus on. I read in a book on blacksmithing that pounding roofing nails into a board can help refine control. Do you agree with that ?

Ok so here is my second try at making a pair of lightweight tongs. Here is one half ready for punching and forming. I started with a 3/8ths bar and put two dents halfway through it with the corner of the anvil. Then I flattened out the pivot part of the tongs and then flipped 90 degrees to flatten out the jaws. I then bent the pivot and jaws to 45 degrees and then bent the jaws back 45 degrees. I have another side to do then drilling and riveting. This is my first real smith project that is more than just messing around. What do ya think? One question I would have for some of the experienced smiths is how I can reduce the number of hammer marks and make a smoother surface. Is that just a matter of practice?

I calculated that the total area of the air holes in the pipe exceed 200% of the area of the bell reducer itself. As for drag, that could be a good point, I dont know. The burner works like a champ out of the forge, its only in the forge that it suffers burning rich but when I dump raw air into the forge, it works like a dream. It seems similar to a link someone sent me in the process showing furnaces that worked by dumping air and gas separately into the chamber and igniting them individually. However this would be safer because even if the burner burns rich, it still burns off the vast majority of the propane. I was referring to the ITC-296A as described at the following link: http://www.budgetcastingsupply.com/ITC.php I applied the ITC-100 like frosting a cake thin. It took a bit of effort but we got it done. The problem is the surface isnt really smooth, being very much like a cake. Another layer might allow me to get it polished smooth which might help reflectivity. That is why I was thinking of the ITC-296A.

yeah I planned it that way but I was sort of upside down in my thinking I think. I am a newbie to smithing. I also wasn't able to flatten nice and straight like I wanted but that is another issue. I still need a ton of practice I know but watching vids isn't quite getting me some of the finer points of how to keep things straight or straighten them later. All advice is appreciated.

I am a newbie to smithing and I have made a first, flawed attempt at some tongs. Some of the mistakes I made I understand but I also had a couple questions. In the attached image I have two issues that i couldnt figure out how to solve immediately. First of all, on the place indicated by A, there is a dent in the side of the metal. What would be the best way to remove that divot to get the side flat. While we are talking about flattening, on the side marked by B, the side is rounded but I would rather have it be straight. Is there a way to straighten that side without curling the metal from A to B? Thanks in advance.

Well it has been a long road to get started. At times I have felt so frustrated I had been tempted to throw in the towel. I tried a dozen burner designs and had a hard time with the blown burner designs working properly and staying lit. Perhaps that was a function of altitude or the need to have the burners be small. I also had Venturi burners that couldn't do much more than bake a cookie in the forge. Eventually I hit on a winner. I originally cast the forge to be powered by three Venturi burners and made it so you could pass through stock or even reduce the size of the forge with fire bricks. Hence I had three burner holes with 1 3/8 inside diameter. However it quickly became apparent that this might not work. The Venturi burners had a bit of trouble burning completely and were just too slow to heat. The solution was a hybrid one. The main burner, in the middle, is a Venturi burner based on my black iron pipe burner with a flame stabilizer instead of a flare. The diameter of the burner pipe is 1 inch inside and it has a 1/2" inside diameter pipe welded inside in the direct center as a flame stabilizer. On the two remaining holes we have air feeds. So while the burner is Venturi, the forge can be and usually is blown. The idea is that the blower (hairdryer for now but blower when I get the cash, is mounted in the pipes and the T junction splits the stream to the front and back pipes. This feeds raw air into the forge which massively increases the heat output of the single venturi burner. Using this design I can get it glowing in about 15 minutes with 5 to 10 psi of propane coming through the Venturi. I plan to add ball valves so I can control the balance of air feed directly. I also thought it might be better to use some 45 elbows and try to avoid having the air stream take 90 degree bends but I am not sure that is necessary, I tried gate valves but the problem is I cant see the position of the valve from the outside so ball valves seem a better fit. I would also like to get some hard brick for the floor instead of the soft but my ceramics supplier is fresh out. I am working on a dedicated table for the forge. Right now it is sitting on my heavy duty welding table (that thing could hold a car if you could get it up there). I want to put a roller holder out front that can be adjusted for length (sort of like trailer hitch style) with a pin through a pipe for a roller. I also need to weld some brick supports that can wrap around and hold a fire brick in a more elegant manner than stacking them like blocks. Another thing I would like to do is weld some 3 inch wide fins in a radial pattern to act as a heat sink on the top and sides as the metal shell stays hot for hours. Finally I want to increase the ITC100 layer to about 1/8th inch thick with perhaps another ITC coating over that for heat retention. Right now the floor has no ITC100 but that will come about. Anyway comments and suggestions are appreciated. I would like to also thank all the people that helped me out and offered encouragement even when I was frustrated beyond belief.

Honestly I wouldnt know where to look in the Library. I have a masters in Computer Science, not mechanical engineeing (these days I think that is unfortunate)

Is there any graph in particular you are referring to? Do you know one for diffusion into steel?

I am not so interested in swords and knives as I am in making tooling. Thanks for all the great information.

I had heard that if you pack red hot steel into charcoal and let it slowly cool that it will take in carbon during the annealing process. If that is true then if you do it enough it stands to reason that it would turn low carbon steel to high carbon steel. Is this true? If not, then is there a way to add carbon to steel in the home shop without melting it down? Finally, is there a way that someone in a home shop could determine the exact carbon content of a piece of steel?

When working on my current forge, I put a thin layer maybe 1/16th of an inch thick of ITC-100 on the forge on the top and walls, not so much on the bottom since fire brick sits there anyway though it might not be a bad idea. I was wondering if you call think that is thick enough or whether I should get some more and make it a bit thicker. If so how thick. Also I dried the ITC100 through slow firing the forge. Do you think I should have let it air dry first before firing? If so I can do that with a second layer.

Perhaps both. It definitely heats better with the ITC without the extra air but the air punches it up a notch. I only used a thin coating, maybe 1/16th of an inch, of ITC. I am debating acquiring more.

Success. Just when I was about to give up, I trued a couple more things. As you recall my forge is casted for three burners and yet I have built only one to date. None of the blown burners worked properly but I was able to get a venturi to stay lit. That torch was a modified version of my first black iron pipe burner with a bigger nozzle and a flame stabilizer instead of flare. So I put that in the forge and then lined the forge with ITC100 and then fired it. I went slow at first to cure the ITC100. Then I buttoned up the back doors and the venturi went yellow in its burn. Then I had a moment of inspiration. I took the hair dryer and pointed it at one of the unoccupied burner holes and the forge started to ROAST hot. Producing very little CO and not too much dragons breath. The venturi was in the middle slot and we had the hair dryer in the back one. We also tried the dryer in the front one with similiar heat but slightly different convection in the torndo (heating the back more than front. So if you put the hair dryer in, it heats more the opposite hole you put it in. So I was able to get the metal up to yellow hot. In the process the ceiling exhaust fan was perfectly able to vent any collected CO and it remained pegged at 0. So here is the system we are rigging up. We have the venturi in the middle and on the two sides will be pipes carrying air being injected directly into the burner. We will have two pipes through individual gate valves up to a T junction. In the T junction I will put in a 2" bell reducer and nipple so I can just set the hair dryer in there til I get a real blower and then I will attach the blower there. I will be able to adjust air flow balance through the two gate valves and the heat will come through the venturi. It is something of a blown forge where air is forced right into the burn chamber rather than into the burner. I will post a video when I have it done and polished. I need to weld on some holders with set screws to hold the burners and air tubes in place and put on some finishing touches, not to mention a new table for it since I want my welding table back.

Well I just fired it for over an hour with a 1" Venturi burner. It made my garage over 120 degrees but didn't raise the temp of the forge beyond baking a couple cookies temp. It seems I poured it way too large. Perhaps I can use it to anneal or something. As it is, the prospect of going to solid fuel is looking better and better. If I cant get that working then I guess I am xxxxxx. But I do hate being out the cash for the propane forge. Live and learn I guess. perhaps it is time to go old school again (and I mean old before Coal and Coke were popularized) to charcoal.

I have the forge designed so I can put insulating fire brick into it. I have thought of putting some in the back and pushing forward to get a much smaller volume. The long and short of the thread is that I am going back to atmospheric. Less factors to juggle, less danger (propane cant pool easily because it draws its own air). I will just have to get the right burner designs and move on. All the failures, expenses and dangers have finally overcome me. At least I got my atmospheric burners to work. I wonder if I can layer the floor with insulating brick and reduce volume even more. It is insulating fire brick though so I don't know how well that will work. Anyone know whether there would be problems using paver bricks for hard bricks? I have a bunch of pavers left over from doing my driveway and thought they might work nice if they can take the heat.

Update. I got one burner to be stable enough to run in the forge by changing the size of the nozzle to a 1/16th inch hole. The burner caused a significant tornado of blue flame in the forge. Interestingly I didnt see much flame comming directly out of the burner but only the constant tornado of blue burning gas. I also managed to flash burn my face lighting the xxxx thing. It put in too much propane too fast in a confined space and when I lit it, it flashed right into my face. At least I had eye protection and my welding jacket on but I feel appropriately singed and chastized. At any rate I let it run for a good half an hour and it got hot in there like an oven but nothing impressive, certainly nothing strong enough to actually heat something red hot. So I guess for whatever reason that isnt going to work. Although the burner was stable, the result was less than impressive. I was hoping I could use this forge as a furnace as well but its pretty clear that it wont get that hot with the current blown burners. In addition the forge puts out so much flame out the front and with periodic pulses of flashing yellow that it just isnt really usable like that. Perhaps I made a mistake in trying to induce a tornado effect in the poured forge. A any rate it seems that the forge just wont get hot with the given burner setup. A very frustrating project -- and not the one I wanted to be working on. I wanted to be working on a railing for my front patio and stairs. Instead I am still working on heating.

the problem is my neighbors. Charcoal was bad enough but with coal and coke I would not only be damaging my health but probably get all my neighbors hating me. I am about to throw in the towel completely. I cant get any burner to work and I cant go solid fuel. It looks like I might have wasted a lot of money for xxxx that will sit around unused. I wonder if I could sell off the forge or something. Get some of my money back and take up knitting or something.